00:02
Let's start by subtracting 4 in both sides.
00:05
So we have the following.
00:09
And now we can factor.
00:11
So we need two numbers, or our key number, is 2 times, or a times c, which is 2 times negative 8.
00:19
So we want 2, or sorry, 2 times 4, which is equal to negative 8.
00:24
We want two numbers whose product is equal to negative 8, and whose sum is equal to a b, which is 7.
00:33
Okay, so we can use 8 and 1, but we'll take negative 1, and we meet the following requirements.
00:44
So we can rewrite this as 2v squared minus v, and then plus 8, b minus 4 is less than 0.
00:54
Now let's fact out a v from our first two terms, and a 4 from our last two terms.
01:07
And now we can factor by grouping.
01:10
So we get 4 plus b, and then 2v minus 1.
01:15
Is less than 0.
01:17
Now let's create our sign graph.
01:19
We have negative 4 and 1 half.
01:23
That's 0 .5.
01:25
And now we'll write our two factors here.
01:31
And now let's choose number to left of negative 4...